1. Field of the Invention
The present invention relates to processes for dehalogenating waste or contaminated materials containing halogenated organic compounds, such as transformer oils, dielectric fluids, wood preservatives, halogenated by-products from the manufacture of halogenated herbicides and soils contaminated with discharges of these materials.
2. Information Disclosure Statement
Polychlorinated biphenyls (PCBs) have shown great utility for use in dielectric fluids, due to their outstanding thermal stability, resistance to oxidation and chemical agents, as well as excellent electrical insulating qualities. However, the discovery of PCBs in environmental samples and subsequent recognition of their potential toxic hazards resulted in restricted sales of PCBs to application in closed electrical systems, and ultimately to the termination of PCB production in 1977.
PCBs represent only one of a large number of halogenated organic compounds that are currently stored for want of an economical and effective means of disposal. Storage of such chemicals, however, is only a stopgap measure. Storage capacity is not unlimited and the quantity of hazardous chemicals generated by industry continuously increases. Thus, effective and affordable methods for destroying halogenated organic compounds are needed.
The difficulty in decomposing halogenated organic compounds arises from the great stability of the carbon-halogen covalent bond. The energy of a carbon-chlorine bond, for example, is on the order of 84 kcal/mole. Thus, many halogenated organic compounds resist biodegradation as well as most chemical decomposition methods. Most known chemical methods achieve only partial dehalogenation, and involve the use of expensive reagents, inert atmospheres, elevated temperatures, complex apparatus, substantial energy consumption or other undesirable parameters. Physical means of disposal have similar problems. Incineration requires substantial energy consumption and complex equipment and may form residual ash, which may require additional treatment.
Thus, there is a need for effective and economical processes for the decomposition of halogenated organic compounds. Chemical processes have shown some promise for such applications. An ideal chemical process would allow very substantial dehalogenation of halogenated hydrocarbons at low cost, using limited reagent, time and energy resources.
The problems associated with disposal of halogenated organic compounds are well known in the art. Chemical processes for dehalogenation of various hydrocarbons have been described.
Howard et al., U.S. Pat. No. 4,327,027, describes a method for chemical detoxification of toxic chlorinated aromatic compounds comprising incubation of such compounds at elevated temperatures with an amount, in excess of stoichiometric, of alkali metal alcoholates of alkanols, alkoxyalkane glycols, alkanepolyols and monoalkyl ethers thereof.
Pytlewski et al., U.S. Pat. No. 4,349,380 discloses methods for recovering metals from chemically combined forms through the use of alkali metals with polyglycols with at least 4 carbon atoms or polyglycol monoalkyl ethers with at least 5 carbon atoms, and oxygen.
Pytlewski et al., U.S. Pat. No. 4,337,368 relates to the use of alkali metals with polyglycols with at least 4 carbon atoms or polyglycol monoalkyl ethers with at least 5 carbon atoms and oxygen to decompose halogenated organic compounds.
Hatano et al., U.S. Pat. No. 4,351,978 relates to a method for dechlorination of PCB via hydrogenation, and employing an alkaline aqueous/alcohol solution, molecular hydrogen and a hydrogenation catalyst.
Brunelle et al., U.S. Pat. No. 4,353,793 discloses a method for removing PCBs from contaminated nonpolar organic solvents using monocapped polyalkyleneglycol alkyl ethers with alkali metal hydroxides.
Cook et al., U.S. Pat. No. 4,387,018 describes a method for extracting PCBs from oil using methanol.
Pytlewski et al., U.S. Pat. No. 4,400,552 discloses a method for decomposing halogenated organic compounds using a reagent comprising the product of the reaction of an alkali metal hydroxide with a polyglycol with at least 4 carbon atoms or a polyglycol monoalkyl ether with at least 5 carbon atoms.
Pytlewski et al., U.S. Pat. No. 4,417,977 relates to methods for removing halogenated organic compounds from organic functional fluids through the use of alkali metals with polyglycols with at least 4 carbon atoms or polyglycol monoalkyl ethers with at least 5 carbon atoms and oxygen.
Pytlewski et al., U.S. Pat. No. 4,430,208 describes a three step process for the removal and detoxification of PCBs from contaminated dielectric fluids. The process comprises extraction with polyethylene glycol followed by extraction with cyclohexane, followed by incubation with a reagent derived from the reaction of sodium or sodium hydroxide, polyethylene glycol and oxygen.
Peterson, U.S. Pat. No. 4,447,541 discloses a method for reducing the halogen content of highly-halogenated organic soil contaminants through the use of an alkali reagent, such as an alkali metal hydroxide, an alkali metal hydroxide/alcohol or glycol mixture, or an alkoxide, in conjunction with a sulfoxide catalyst.
Tundo, U.S. Pat. No. 4,632,742 discusses a method for decomposing halogenated organic compounds through an anaerobic process using Nixolens (R), alcohols, polyethylene glycols or polyglycol monoalkyl ethers with at least 5 carbon atoms, together with an oxidizing agent.
Weitzman, U.S. Pat. No. 4,662,948 relates to a method for removing PCBs and dioxins from soils through extraction of soils with a mixture of halogenated hydrocarbons and a polar solvent.
Pytlewski et al., U.S. Pat. No. 4,460,797 discloses a method for the decomposition of halogenated organic compounds using a reagent comprising the product of the reaction of an alkali metal hydroxide with a polyglycol with at least 4 carbon atoms or a polyglycol monoalkyl ether with at least 5 carbon atoms.
Pytlewski et al., U.S. Pat. No. 4,471,143 relates to a composition of matter in liquid form comprising a coordination complex which is the product of the reaction of an alkali metal or alkali metal hydroxide with a polyglycol with at least 4 carbon atoms or a polyglycol monoalkyl ether with at least 5 carbon atoms.
Heller, U.S. Pat. No. 4,483,716 discusses processes for removing chemical substances, including halogenated organic compounds, from porous substrates, using a poultice comprising particulate matter and a volatile solvent, then destroying such halogenated hydrocarbons using the product of the reaction of an alkali metal or alkali metal hydroxide with a polyglycol with at least 4 carbon atoms or a polyglycol monoalkyl ether with at least 5 carbon atoms.
Pytlewski et al., U.S. Pat. No. 4,523,043 relates to reagents and methods for decomposition of organic sulfur-containing compounds through the cleavage of carbon-sulfur bonds using the product of the reaction of an alkali metal or alkali metal hydroxide with a polyglycol with at least 4 carbon atoms or a polyglycol monoalkyl ether with at least 5 carbon atoms.
Pytlewski et al., U.S. Pat. No. 4,602,994 discloses a method for the removal of halogenated organic compounds from organic functional fluids using, in an inert atmosphere, the product of the reaction of an alkali metal or alkali metal hydroxide with a polyglycol with at least 4 carbon atoms or a polyglycol monoalkyl ether with at least 5 carbon atoms.
Mendiratta et al., U.S. Pat. No. 4,663,027 relates to a method for removing polyhalogenated hydrocarbons from nonpolar organic solutions by admixing flakes or pellets of an alkali metal hydroxide with such a solution to form a slurry of alkali metal hydroxides of uniform size, followed by reacting such slurry with a polyalkylene glycol or a monocapped polyalkylene glycol alkyl ether.
Mendiratta et al., U.S. Pat. No. 4,748,292 discloses a method for removing polyhalogenated hydrocarbons from nonpolar organic solutions, which uses, in an amount at or exceeding stoichiometric to the total number of halogen groups, a reagent comprised of an alkali metal hydroxide and a polyalkylene glycol or a monocapped polyalkylene glycol alkyl ether.
Way, U.S. Pat. No. 4,764,256 describes a method for the removal of PCBs from contaminated oil, through the use of continuous solvent extraction.
Streck et al., U.S. Pat. No. 4,776,947 discloses a method for dehalogenation of halogenated organic compounds in hydrocarbon oils through the use of alkali or alkaline earth alcoholates having at least 6 carbon atoms.
Many of the previous references have involved the use of a reagent derived from the reaction of an alkali metal or alkali metal hydroxide. These references teach the combination of such a reagent, in an amount at or above stoichiometric with respect to the total number of halogen groups, with a solution containing the contaminating halogenated hydrocarbon. Most teach the use of substantially elevated temperatures.
Airs et al., British Patent Specification 618,189 discloses dehydrohalogenation of dihalogen alkenes and monohalogen alkenes to produce alkynes through the use of glycol monoalkylether alcoholates.